Allow --enable-* options in configure.
Allow --enable-* options in configure.

jpflori/flint2,dsroche/flint2,fredrik-johansson/flint2,dsroche/flint2,wbhart/flint2,jpflori/flint2,fredrik-johansson/flint2,wbhart/flint2,jpflori/flint2,jpflori/flint2,wbhart/flint2,dsroche/flint2,fredrik-johansson/flint2,dsroche/flint2